Field of the Invention
The present invention relates to an imaging device.
Description of Related Art
In Japanese Unexamined Patent Application, First Publication No. 2014-135535, a solid-state imaging device which has a plurality of stacked substrates and is capable of obtaining visible light images and infrared light images at the same time has been disclosed. FIG. 11 shows a configuration of a solid-state imaging device 1000 in this related art. A cross-section of the solid-state imaging device 1000 is shown in FIG. 11. As shown in FIG. 11, the solid-state imaging device 1000 includes a first substrate 700, a second substrate 800, and a visible light cut filter 900. The first substrate 700 and the second substrate 800 are stacked in a thickness direction D11 of the first substrate 700.
The first substrate 700 includes a first semiconductor layer 710, a plurality of color filters 720R, a plurality of color filters 720G, and a plurality of micro-lenses 730. In FIG. 11, a reference numeral of one micro-lens 730 is shown as a representative.
The first semiconductor layer 710 includes a plurality of first photoelectric conversion units 711. In FIG. 11, a reference numeral of one first photoelectric conversion unit 711 is shown as a representative.
The plurality of color filters 720R and the plurality of color filters 720G are arranged on a surface of the first semiconductor layer 710. The first substrate 700 further includes a plurality of color filters 720B shown in FIG. 12. In FIG. 11, the plurality of color filters 720B are not shown. The plurality of micro-lenses 730 are arranged on surfaces of the plurality of color filters 720R, the plurality of color filters 720G, and the plurality of color filters 720B.
The second substrate 800 includes a second semiconductor layer 810. The second semiconductor layer 810 includes a plurality of second photoelectric conversion units 811. In FIG. 11, a reference numeral of one second photoelectric conversion unit 811 is shown as a representative.
The visible light cut filter 900 is disposed between the first substrate 700 and the second substrate 800. Light passing through the plurality of first photoelectric conversion units 711 is incident on the visible light cut filter 900. The visible light cut filter 900 blocks visible light included in the incident light.
FIG. 12 shows an array of the plurality of first photoelectric conversion units 711. FIG. 13 shows an array of the plurality of second photoelectric conversion units 811. In FIG. 12 and FIG. 13, the thickness direction D11 of the first substrate 700 is a direction perpendicular to a sheet of each figure. In FIG. 12, a reference numeral of one first photoelectric conversion unit 711 is shown as a representative. In FIG. 13, a reference numeral of one second photoelectric conversion unit 811 is shown as a representative. In FIG. 12 and FIG. 13, positions of the plurality of color filters 720R, the plurality of color filters 720, and the plurality of color filters 720B are indicated by dashed lines. In FIG. 12 and FIG. 13, reference numerals of one color filter 720R, two color filters 720, and one color filter 720B are shown as representatives. The plurality of first photoelectric conversion units 711 and the plurality of second photoelectric conversion units 811 are arranged in a matrix. In addition, the plurality of color filters 720R, the plurality of color filters 720G, and the plurality of color filters 720B are arranged in a matrix.
Light from a subject which has passed through an imaging lens disposed optically forward of the solid-state imaging device 1000 is incident on the plurality of micro-lenses 730. The plurality of micro-lenses 730 collect light passing through the imaging lens. The plurality of color filters 720R, the plurality of color filters 720G, and the plurality of color filters 720B transmit light having a wavelength corresponding to a predetermined color in visible light. The plurality of color filters 720R transmit light having a wavelength corresponding to red, that is, red light. The plurality of color filters 720G transmit light having a wavelength corresponding to green, that is, green light. The plurality of color filters 720B transmit light having a wavelength corresponding to blue, that is, blue light. In general, infrared light passes through the plurality of color filters 720R, the plurality of color filters 720G, and the plurality of color filters 720B.
Each of the plurality of first photoelectric conversion units 711 is arranged in a region corresponding to any one of the plurality of color filters 720R, the plurality of color filters 720G, and the plurality of color filters 720B. Light passing through each of the plurality of color filters 720R, the plurality of color filters 720G, and the plurality of color filters 720B is incident on any one of the plurality of first photoelectric conversion units 711. A first photoelectric conversion unit 711 disposed in a region corresponding to the color filter 720R generates an R signal based on the red light. A first photoelectric conversion unit 711 disposed in a region corresponding to the color filter 720G generates a G signal based on the green light. A first photoelectric conversion unit 711 disposed in a region corresponding to the color filter 720B generates a B signal based on the blue light.
Each of the plurality of second photoelectric conversion units 811 is disposed in a region corresponding to any one of the plurality of color filters 720R, the plurality of color filters 720C and the plurality of color filters 720B. Light passing through the plurality of first photoelectric conversion units 711 is incident on the visible light cut filter 900. Light the visible light of which has been blocked by the visible light cut filter 900 is incident on the plurality of second photoelectric conversion units 811. The plurality of second photoelectric conversion units 811 generate an IR signal based on the infrared light.
First photoelectric conversion units 711 disposed in regions corresponding to the color filter 720R, the color filter 720G, and the color filter 720B absorb some infrared light. For this reason, the first photoelectric conversion units 711 generate an R signal, a G signal, and a B signal containing components based on the red light, the green light, and the blue light respectively and a component based on the infrared light. These R, G, and B signals are corrected by an IR signal generated by the second photoelectric conversion unit 811, and thereby it is possible to obtain an R signal, a G signal, and a B signal from which the component based on the infrared light is removed. The solid-state imaging device 1000 can obtain a signal by removing the component based on the infrared light from a signal containing the components based on the red light, the green light, and the blue light and the component based on the infrared light using the above method. Furthermore, the solid-state imaging device 1000 generates visible light images based on these signals.
As described above, the first photoelectric conversion unit 711 disposed in a region corresponding to each of the color filter 720R, the color filter 720G, and the color filter 720B absorbs some infrared light. For this reason, an R signal, a G signal, and a B signal generated by the plurality of first photoelectric conversion units 711 contain a component based on the infrared light. In FIG. 12, the first photoelectric conversion unit 711 which generates the R signal containing a component based on the infrared light is described as “R+IR” in the vicinity thereof. In FIG. 12, the first photoelectric conversion unit 711 which generates the G signal containing a component based on the infrared light is described as “G+IR” in the vicinity thereof. In FIG. 12, the first photoelectric conversion unit 711 which generates the B signal containing a component based on the infrared light is described as “B+IR” in the vicinity thereof.
Therefore, it is necessary to correct the R signal, the G signal, and the B signal which are generated by the plurality of first photoelectric conversion units 711 using an IR signal generated by the second photoelectric conversion unit 811 to generate a visible light image. The corrected R signal is expressed by Equation (A1). The corrected G signal is expressed by Equation (A2). The corrected B signal is expressed by Equation (A3).R′=R−αIR(r)  (A1)G′=G−βIR(g)  (A2)B′=B−γIR(b)  (A3)
In Equation (A1), R′ is a value of the corrected R signal, and R is a value of the R signal before the correction. In Equation (A1), a is a coefficient. In Equation (A1), IR(r) is a value of an IR signal generated by the second photoelectric conversion unit 811 disposed in a region corresponding to the color filter 720R. In FIG. 13, the second photoelectric conversion unit 811 which generates the IR signal (IR(r)) is described as “IR(r)” in the vicinity thereof.
In Equation (A2), G′ is a value of the corrected G signal, and G is a value of the G signal before the correction. In Equation (A2), β is a coefficient. In Equation (A2), IR(g) is a value of an IR signal generated by the second photoelectric conversion unit 811 disposed in a region corresponding to the color filter 720G In FIG. 13, the second photoelectric conversion unit 811 which generates the IR signal (IR(g)) is described as “IR(g)” in the vicinity thereof.
In Equation (A3), B′ is a value of the corrected B signal, and B is a value of the B signal before the correction. In Equation (A3), γ is a coefficient. In Equation (A3), IR(b) is a value of an IR signal generated by the second photoelectric conversion unit 811 disposed in a region corresponding to the color filter 720B. In FIG. 13, the second photoelectric conversion unit 811 which generates the IR signal (IR(b)) is described as “IR(b)” in the vicinity thereof.